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Radar terrain signal simulator
| Details |
Inventors: Heidrich, Arthur J.;
Assignee: General Electric Company (Fairfield, CT)
Primary Examiner: Hubler; Malcolm F.
Assistant Examiner:
Attorney, Agent or Firm: Amgott; Allen E.
To simulate the radar return from terrain of particular generic type (e.g. desert, forest, cultivated land) it is a known suggestion to employ closed-loop shift register with feedback suitable to produce particular "texture" of return from specified terrain. It is here disclosed to synchronize output of such register with azimuthal position of simulated search radar; but this alone gives "grainy" effect because "smeary" or slowly changing amplitude with range in PPI sweep is not matched by corresponding lateral, or azimuthal, "smear". This objectionable effect is overcome by providing three sets of output terminals on feedback register, giving outputs corresponding to shifts for azimuths N, N+1, and N+2. By buffing together the three outputs, an azimuthal variation at a slow rate, comparable with the variation with range, is obtained, giving a more deceptive (and thus better) simulation. |
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DETAILED DESCRIPTION A shift-register is provided, with feedback which will provide a pseudo-random output that simulates the appearance of radar returns from given terrain, when fed clock pulses of suitable frequency.
By "pseudo-random" is meant an output which is actually cyclically repetitive, but has a period sufficiently long that its repetitive parts will be sufficiently separated in space or in time so that an observer will not become aware of their repetitive nature by casual observation.
(Because the term "feedback" as an adjective has acquired a number of somewhat different meanings in the art, a register as described will be designated a fedback register.
) The apparatus in which the present invention is principally intended to be used is a simulator comprising a store of data which includes peak and valley lines of the terrain whose radar image is to be simulated, together with indication of the radar reflectivity of the various surfaces of the terrain, and an identification of the nature of the terrain.
A plan position indicator (PPI) presentation device is provided, with means to produce a sweep in range from an origin representing the location of the radar system being simulated.
By data processing equipment the intensity of the radar return from each part of the simulated terrain is calculated, and the presentation is illuminated correspondingly.
However, as a matter of economy, it is undesirable to store terrain data in such volume as would be required to simulate the particular texture of return which the skilled operator would recognize as a characterizing a particular kind of terrain, such as woodland, cultivated land, and the like.
The pseudo-random output of the feedback shift register is applied to modulate the brightness of the sweep, producing an irregularity consistent with the particular terrain being represented.
The appropriate pseudo-random output may be gated in accordance with the stored identity of the kind of terrain; different such outputs may be produced from separate fedback shift registers, having different feedback paths; or the feedback paths of a single shift register may be altered by gating
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Radio 
